Ferrite rotator



Feb. 18, 1958 s. SENSPER 2,824,288

FERRITE ROTATOR Filed May 2, 1955 2 Sheets-Sheet l I Ann-1 2s [2A I :7 l WW I {/2 RF I PU 1 50 I6 18 2 RF ourpur k L F1 l.

POWER SUPPLY POWER 1 CONTROL SUPPLY RF/NPUT a, L MEANS RF OUTPUT I CR Y5 TAL OUTPUT 2 /NVEN7'OR i I SAMUEL SENS/PER E9 4 56L 7 BY A TTORNEY Feb. 18, 1958 Filed May 2, 1955 S. SENSIPER FERRITE ROTATOR 2 Sheets-Sheet 2 b -l /38 I0 75 2 P o WER R F y5 /1EA TING: COIL S UPPL Y INPUT TERMINALS co/v TROL Z I MEA NS 0U TP U r 4 s 01. ENwTERMlNALs 26 L 1, P o WER i I 3 I SUPPLY kHz/1 rnva COIL TERMINALS SOLENOID TERMINALS L I 24 PHASE 7 POWER COMPARA TOR SUPPL Y 164 I I I PHA SE To COM/3A M R //v VEN TOR SA M U'EL S ENS/PEI? Fia- ATTORNEY zgszegzas RoTAroR Samuel Sensiper; nos A ngeles; Califi assignor to Hughes Aircraft Company; Shiver Gity, Califi, a corporation of Delaware I Application May2;t1'9"55; steam. 505,328

Clainis;- (Cit-333 173 invention relates. to electromagnetie propagation structures and' more particularly to a device f0l== r0tatin gf the plane of polarization of" air -electromagnetic wavez A' ferromagnetic ceramic body commonly kn'owm as a ferrite isoften emplloyedtorotatetheplane of polariza tion of Ta linearly polarizedelectromagnetic wave.- To this endga ferritebodyis disposed-withinwa waveguide which is excited-in a. suit-abley-manner to propagate'cira cularly polarized waves- A unidirectionai-axialxmagnetic field is maintained throughout: the ferrite body: andthe rotation of the. plane. of polarization is produced by an effect known as the-Faraday elfect; The-combination oftheferrite body, thewaveguide,- and the' magneticfield producingrmeans is :commonly: called a: ferrite: rotator; Such; a rotator is describedand: claimed in: copendin'g application Serial No. 4-19;259;:. entitled Waveguideisolator lf filed March 29,! 1 954;lby-.-W; Ac Hughes; and assignedlto theasigneeoflthepresentinvention,

The amount of rotation producedt'byta:ferrite= rotat6r is afunction. 'of I axiahmagnetic field strength9- However, maximum rotationeis gen'erally.desiredandiforithis reason a ferrite is. normally, operated at saturation-2 Atitlie'field strength required to produce: saturatiom and at field strengths substantially above that: required? to produce saturation," attenuation is:- encount'ered within. a certain frequency: range because 0% a phe'nOmenOm which i well-known property-of a: ferrite. lmsuclna cas'e, the

precession of an electron in--the crysta'lline structure of is very. close it not equal tor the field streng'tli required" to. produce gyro-resonancei-ae theSebandt- At present no known methodr-has: zbeen' devised ltor overcometliifilimit'? tion of a ferrite 'rotat'o'n It is; therefore an; *objfect ofr:ther inventiontw provide animproved ferrite-rotate I It is another object of therinventioni to rovide: aaprae ticalgiferrite rotator: femoper'atiorrz at the S ba ndt Forv the p'art-iculara. case": of: the elongated rod -slfa ferrites whiclnare: currently employed in rotatorsi it knownv thatt-h'efrequencyrat. whichr maximnm attenu'a tion' occurs in a:territe decreases witlt the saturation mag? netizationt ofet-he ferrittaz. Itiis alse; known that 'tlie--sa"titra" tiorrv magnetization: :of aa ferrite "deerea'ses with tempera ture.- In. accordance'rrwithze the invcntion; a ferri'te Body is appropriately}, positionedrinsidwof -a: waveguide'wxfd uniform axial magnetic-"field is ntaintained wi ferrite;body;i-througliout iikiengtlrzafin the se ofch'm- 2 v viddiit addition to heat theferr-ite body tovreduceits saturation magnetization wherebythe frequeney at which maximum attenuation occurs may; be reduced: to avalue suBstantia-lly Below the'S-h and The novel features; which are believed to bech-arac teristic ofvthe invention,. both asto its organization and method of operation together with further objects and advantages thereof, will be better understood from: the following' description considered inconnectionwith the accompanying drawings inwhich-r several embodiments ofi 'the. inventionareillustratedby wayof example. It is to: lie expressly understood-; however;- that: the drawinges are for the purpose of illustratioirand description only, and are not-intended as a definition ofthe limits of tlie inventione Fig: I'is asectional view ofia ferrite-rotator incorporating-the 1 present; invention;-

Fig. 2' is: a sectional view at a ferrite rot'ator provid'ecliwith automatic temperature control means in accordance with the present inventiong.

g, Fig. 3' is 'a schematic representation-and circuit diagram of a ferrite rotator incorporating the presentinvention' provided. automatic temperature control means"wliich respondt'o changes in the rotation" of a wave'passi'ng, through the roltator;

Pi"? 4i'sf ascctionaiview onthe line 4-4' ofFig. 3; Fig; Sis' a-graph characteristicof-the operation of'the temperaturegcontroi'means of Fig; 3;

Fig dis a schematic side view and circuit diagram of af'ferr fe rot'a'tor incorporatingtthe present invention and utilizing control means and a' phase sensing means diiferent from that shown in Fig. 3 for controlling. the temperature'oftheferrite body thereof; and n 'Fi 7isalsectibnal viewon' the line 77 of Fig 6.

R efe ingto the drawings, a ferrite rotator 10 is shown =c'o'tnprising a cylindrical Waveguide 11in which 'a -fer te"iody=1 $=iscentra1lyposition'ed'by two dielectric supp ting dis'c's 16 and1 8. A'non=inductive Wound heatin; do 20 is thendis osed about the waveguide- 12 w ithinceramic insulating cylinder 22 Uispo sed outside -ofiand contiguous to theinsulatingwylinder 22 is acsolenoid-z'fit which is employed to" produce" an" axial magnetic field through the ferrite :b'ody 1 Solenoid 24 is: accordingly supplied'with direet currentby a potential source- 26:, Hea'tingcoil 20 is' supplied ivith direct ourrent b ymea'ns of a heatingi sourceiofipotential zii. 1 The centra-l-por-tion' 30 ofthe waveguide IZ' is insulated, for exam-pie, by: dielectric discs as: shown from two: sep arate input and output portions-32: and: 34 "respectively; although this-neednot necessarily bedoneif temperatures employed within the central portionfitl of the waveguide 12"ar"e not too high and do not disturb: the operation of adjacent equipment or equipment connected tothe inputand outputportion's 3 2 and 34 of the waveguide 121 The operation of the ferriterotator 10 is exactly the same as that of ferrite rotators'of' the""priorfart e tcept that' ferrit'e rotator 1 Ill-may beused at the S-h'a'nd "where generally substantial attenuation is produced by the ab: stirpti'on of energy by the ferrite body 141 Ac :r'di'rigly; tlie heatingacoil 20 heats the central" portio" 30"'of th'e'" wavegnide l'z andthe ferrite-h dden; I that the saturation: magnetization of the f r- 1- ebod y will decrease-withan increasein the temperature of the fer:

the body- 14*, hence,-- the saturationmagnetiza-tion of the ventiona1..errite rotatorss" However; mem aze pre junctiinnwiilipotefitial source 26. By heating the ten rite body 14 to an appropriate temperature, the frequency at gyro-resonance where substantial attenuation occurs within the ferrite rotator 10 may be reduced to a value substantially below the operating frequency, e. g. theS- band, of the ferrite rotator 10.

For a given field strength, the amount of rotation produced by'the ferrite rotator 10 is sensitive to relatively small changes in temperature. Hence, it may be found desirable to employ an automatic temperature control device whereby the temperature of the ferrite body 14 may be maintained substantially constant or at least the amount of rotation produced by the ferrite rotator 10 may be maintained substantially constant and at an appropriate, predetermined value. In accordance with'this purpose, an automatic temperature control circuit is shown in Fig. 2 in combination with the ferrite rotator 10 which is shown in a broken sectional view comprising solenoid 24, potential source 26, heating coil 20, ferrite rotator 14 and the central portion 30 of waveguide 12. A thermocouple 120 is disposed or buried within the wall of the central portion 30 of the waveguide 12 in order to obtain a voltage proportional to the temperature of the medium immediately adjacent to the ferrite body 14. Power supply control means 122 are then shown connected to the thermocouple 120. Power supply control means 122 are connected to a power supply 124 which is in turn connected to the heating coil 20. A voltage is derived by power supply control means 122 which is proportional to the temperature of the atmosphere about the ferrite 'body 14 and the power supply 124 is thereby operated by power supply control means 122 automatically to increase or decrease the power supplied to heating coil 20 in accordance with changes in the temperature of the atmosphere adjacent the ferrite body 14.

The automatic control circuit of Fig. 2 may sutiice in some cases; however, it may be more practicable in other cases to obtain a voltage proportional to the rotation of a wave produced by the ferrite rotator 10 to control a power supply. Such circuits are shown in combination with the ferrite rotator 10 of the present inventionin Figs. 3 and 6. Referring now to Fig. 3, there is shown a side view of the ferrite rotator 10 including waveguide 12 having the input portion 32 and the output portion 34. A probe 130 is disposedat a predetermined point about the circumference of the output waveguide portion 34. A rectifier 132 is connected to the probe and a resistor 134, across which is connected a capacitor 135, is connected from the rectifier 132 to ground. In order to provide a control voltage, which is proportional to the difference between the actual amount of rotation of a wave passing through the ferrite rotator 10 and a predetermined desired amount of rotation, a biasing source of potential 136 is connected to a power supply control means 138 as is the positive terminal of resistor 134. A power supply 140 is then connected from power supply control means 138 to the terminals of the heating coil 20, not shown in Fig. 3.

Potential source 26 is again shown in Fig. 3 connected to the solenoid 24. A section of the output portion 34 of waveguide 12 is shown in Fig. 4 including the probe 130,-rectifier 132, resistor 134, smoothing capacitor 135, and biasing source of potential 136. The lines 142 within the output waveguide portion 34 represent the electric" flux lines of the electric field of a wave propagated in a TE mode. Assuming the direction of polarization of the wave as represented by the lines 142 indicate the correct direction after the desired amount of rotation of the wave has been produced, an angle is employed to represent an error angle which is undesired. If 0 is the error angle; then -a curve of the output of rectifier 132, which may be a crystalrectifier, is indicated by curve 4 150 in Fig. 5. It is to be noted that curve 150 starts from zero at =-g to a maximum at 0= +2 In order to make the feedback system of temperature control a null seeking system, an error voltage must be provided which is proportional to the magnitude of the error of phase rotation and also proportional to the algebraic sign of the error. Accordingly, potential source 136 provides a voltage V as indicated in Fig. 5 whereby this is accomplished.

In the operation of the circuitry in combination with the ferrite rotator 10 in Fig. 3, the input portion 32 of thewaveguide 12 is excited according to a certain mode of propagation. The ferrite rotator 10 then rotates the wave as it is passed through the central portion 30 of the waveguide 12, not shown. Upon reaching the output portion 34 of the waveguide 12, the probe 130 in conjunction'with the rectifier 132 detects an error angle of rotation, if any exists. Biasing potential source 136 then normalizes this error making the input to power supply control means 138 proportional in algebraic sign and in magnitude to the error angle of rotation of the wave propagated in the output waveguide portion 34. Power supply control means 138 then controls power supply 140 .in accordance with the error detected and accordingly heats the ferrite body 14, not shown in Fig. 3, to a temperature to compensate for the error in the amount of rotation produced by the ferrite rotator 10. Heating thcferrite body 14 thus avoids a substantial amount of attenuation by reducing the saturation magnetization of the ferrite body 14 whereby the frequency at which maximum attenuation occurs for thefield strength necessary to provide the desired amount of rotation is reduced to a value substantially below the operating frequency of the ferrite rotator, 10.

A similar automatic control system is shown in Fig. 6 where the ferrite rotator. 10 is shown in a side view including the waveguide 12 having input and output portions 32 and, 34 and solenoid 24. Because of the side view, the remaining elements of theferrite rotator 10 are not shown. Two probes 160 and 162 are disposed 18f) mechanical degrees about the output waveguide portion 34. These probes are connected to a phase comparator 164 which may be referenced to ground, as shown, as is the output waveguide portion 34. The phase of the signals picked up by the probes 160 and 162 are then throughthe ferritebody 14, not shown.

effect may havesubstantial utility when an average field 7 compared with respect to a reference potential such as ground as shown. "When the waveguide 12 is excited to propagate circularly polarized waves and a predetermined amount of rotation isfldesired, phase comparator 164 to which'the probes 'and 162 are connected may be employed to provide a voltage. proportional in magnitude and in algebraic sign to the magnitude of the error angle of rotation from a predetermined and desired angle of retation. This is. indicated in. Fig. 7 where the angle 0 againis employed to indicate the error angle of rotation, the lines 142 indicating the electric field lines of the wave propagated within the waveguide 12. The section of the output waveguide portion 34 is shown in Fig. 7 with probes 160 and 162. The operation "of the phase comparator 164. is .old and well-known inthe art. A power supply 166 is, sho'wnin Fig. 6 connectedto the phase comparator 164 and.in turn connected to theterminals of the heating coil 2 0,. not shown, and-of the solenoid- 24. A pure heatcontrolservo, which only controls the current through heating coil 20, is obviously very slow to respond. In order. to compensate for small rotation errors, phase comparator 164 may thus be employed to control the power supplied to solenoid 24, whereby compensation may be produced by a change in field strength This -vernier strength somewhat. below saturation is selected.

In the operation of the circuit with the ferrite rotator shown in Fig. 6, a wave is propagated within waveguide 12 through the input portion 32 and rotated by ferrite rotator 10, and the error angle, if any, is detected by the probes 160 and 162. The phases of the signals picked up by the probes 160 and 162 are then compared in comparator 164 which gives an output signal proportional to the magnitude of the error angle 0 indicated in Fig. 7 and proportional in algebraic sign to the error angle. Phase comparator 164 then controls the power supply 166 in response to the error angle at the output waveguide portion 34, and the heating coil 20 and solenoid 24, not shown, are supplied with more or less current as is needed to correct the error in the angle of polarization.

What is claimed is:

1. A rotator for rotating the plane of polarization of a linearly polarized electromagnetic wave comprising a waveguide, a ferrite body disposed within said waveguide, means for producing a unidirectional axial magnetic field through said ferrite body, means for heating said ferrite body to decrease the saturation magnetization of said ferrite body, whereby the frequency at which maximum attenuation occurs within said ferrite body may be reduced to a value below the operating frequency of said rotator, probe means inserted into said waveguide and disposed adjacent to the output end of said waveguide for detecting electromagnetic energy therein, means connected to said probe means for deriving a voltage proportional to the difference between the actual angle of rotation of said wave and a predetermined angle of rotation, and means coupled to said probe means for controlling said means for heating said ferrite body in response to changes in said voltage.

2. A rotator for rotating the plane of polarization of a linearly polarized electromagnetic wave comprising a waveguide, a ferrite body disposed within said waveguide, means for producing a unidirectional axial magnetic field through said ferrite body, means for heating said ferrite body to decrease the saturation magnetization of said ferrite body, whereby the frequency at which maximum attenuation occurs within said ferrite body may be reduced to a value below the operating frequency of said rotator, a probe inserted into said waveguide and dis posed at a predetermined point about the circumference of said waveguide, a rectifier circuit, said probe being connected to said rectifier circuit and means connected to said rectifier circuit for controlling said means for heating said ferrite body in response to the deviations of the actual angle of rotation of said wave from a predetermined angle of rotation.

3. A rotator for rotating the plane of polarization of a linearly polarized electromagnetic wave comprising a waveguide, 21 ferrite body disposed within said waveguide, means for producing a unidirectional axial magnetic field through said ferrite body, means for heating said ferrite body to decrease the saturation magnetization of said ferrite body, whereby the frequency at which maximum attenuation occurs within said ferrite body may be reduced to a value below the operating frequency of said rotator, two probes inserted into said waveguide and disposed substantially mechanical degrees from each other about the circumference of the output end of said waveguide, a phase comparator connected to said probes for producing an error correction voltage proportional to the difference between the actual angle of rotation of said wave and a predetermined angle of rotation, said phase comparator being connected to said means for heating said ferrite body to control said means for heating said ferrite body in accordance with the changes in said error correction voltage.

4. A rotator for rotating the plane of polarization of a linearly polarized electromagnetic wave comprising a waveguide, a ferrite body disposed within said waveguide, means for producing a unidirectional axial magnetic field through said ferrite body, means for heating said ferrite body to decrease the saturation magnetization of said ferrite body, whereby the frequency at which maximum attenuation occurs within said ferrite body may be reduced to a value below the operating frequency of said rotator, probe means connected to the output end of said waveguide and inserted through the wall thereof, means connected to said probe means for deriving a voltage proportional to the difference between the actual angle of rotation of said wave and a predetermined angle of rotation, and means coupled to said probe means for controlling said means for heating said ferrite body and said means for producing a unidirectional axial magnetic field in response to variations in said voltage.

5. A rotator for rotating the plane of polarization of a linearly polarized electromagnetic wave comprising a waveguide, a ferrite body disposed within said waveguide, means for producing a unidirectional axial magnetic field through said ferrite body, means for heating said ferrite body to decrease the saturation magnetization of said ferrite body, whereby the frequency at which maximum attenuation occurs within said ferrite body may be reduced to a value below the operating frequency of said rotator, means for deriving a voltage proportional to the operating temperature of said ferrite body, and control means connected to said means for producing a unidirectional axial magnetic field and to said means for deriving said voltage for operating said means for producing a unidirectional axial magnetic field in response to changes in said operating temperature.

References Cited in the file of this patent UNITED STATES PATENTS 2,434,255 Bond et al Jan. 13, 1948 2,719,274 Luhrs Sept. 27, 1955 2,748,353 Hogan May 29, 1956 FOREIGN PATENTS 511,649 Belgium June 14, 1952 

